Effect of antiscalants on organic fouling potential of rough membrane in membrane distillation: Focusing on the evaluation of interfacial interaction

Abstract

Impacts of antiscalants on fouling potential of rough membranes were explored in membrane distillation (MD) system, and three antiscalants were applied in this study, including 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), diethylene triamine penta methylene phosphonic acid (DTPMPA), and polymaleic acid (HPMA). Deteriorated organic fouling caused by 150 mg/L lysozyme (LYS) solutions was observed with the addition of antiscalants in MD influent, due to variations of surface properties induced by adhesion of antiscalants. In MD operation of LYS solutions, a mild flux drop of 37.7% was obtained for unmodified PTFE membrane, while PBTCA, DTPMPA, and HPMA groups all demonstrated severe flux decline of 58.4%, 46.4%, and 63.5%, respectively. Methods of surface element integration and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory were applied to estimate interfacial interaction among foulants-reconstructed membrane surface. MD membranes initially adhered by PBTCA and HPMA both demonstrated higher surface roughness and correspondingly lower energy barrier, promoting sharper depositions of LYS and faster flux decline. A four-stage pattern was roughly proposed for organic fouling development in MD, which was notably affected by adherence of antiscalants. Comparatively, MD membranes adhered by DTPMPA displayed relatively lower surface roughness and higher interaction energy barrier, suggesting that DTPMPA might be a feasible method for MD fouling mitigation.